Square/round 2 Tier Cake.

I am getting ready to do a two tier Baby Shower cake with a 3-d owl on top..

If I do two tiers with the bottom one being Square and the top being Round do I make them the same size or do I make the Bottom 12" and the Top 10" It will have a 3-D owl sitting on top. I was looking for pictures but haven't seen anything.

Second Question. How would I go about Securing the Owl to the Top Tier? Do I Dowel the snot out of it? DO I build it on a fondant covered cake board? I am open to suggestions.

It depends totally on the look you are going for - either would be fine in my opinion, although you would have to be careful that the owl is proportionate to the rest of the cake.

Again, depending on the size of the owl, either build it on its own little board with some dowels to support it in the tier beneath, or if it is small enough then just a couple of toothpicks to hold it in place.